A third International Hyperthermia Conference is planned to provide for scientific interchange between physicists, chemists, biologists, and clinicians with the objective of evaluating the use of hyperthermia as an agent in cancer therapy. The focus will be research accomplished and problems to be solved. The Conference is organized such that the various disciplines will be interacting together in the same sessions to consider the use of hyperthermia in the clinic as the ultimate goal. Recent data indicate that hyperthermia may have a potential in cancer therapy. Hopefully, a review of the findings since the last Second International Hypethermia Conference will reinforce the potential for hyperthermia and will provide a direction for research and clincal trials. The main objective is to review hyperthermic research conducted since the Second International Conference convened in Essen, Germany, in June 1977. From these findings, we hope to establish if hyperthermia can be expected to serve as a useful modality in cancer therapy. Specifically, the Conference will cover subjects such as: the mechanisms of heat inactivation and heat radiosensitization; aspects of heat combined with chemotherapy and radiation; and the practical aspects of delivering heat, and measuring temperatures in vivo. Particular emphasis will be placed on hyperthermic effects on tumors relative to effects on normal tissues, i.e., the therapeutic gain. The general plan of the Conference is to encourage communication between the basic scientists and clinicians; for this reason, the Conference is planned around concepts and questions rather than experimental systems.